Method and apparatus for forming stretch blow molded containers

ABSTRACT

The present invention relates to a base assembly ( 100 ) for forming a base portion of a plastic container. The base assembly comprises a base pedestal ( 104 ), a base mold attached to the base pedestal, a push rod ( 102 ) movable between a first position and a second position with respect to the base mold to reposition a portion of the plastic container, and an activation mechanism adapted to move the push rod between the first position and the second position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/866,810, filed on Aug. 9, 2010, which is a National Stage ofInternational Application No. PCT/US2007/00800, filed Jan. 11, 2007,which claims priority of U.S. Provisional Application 60/757,889 filedJan. 11, 2006, priority to each of which is claimed, and the contents ofeach of which are hereby incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to a method and apparatus forforming blow molded plastic containers. More particularly, the presentinvention relates to a method and apparatus that utilizes a movable,in-mold structure for displacing a portion of the blow molded container,such as the base.

Related Art

Conventionally, a container may be manufactured through a process knownas blow molding. In blow molding, a parison is received at a blowmolding apparatus, and the parison is enclosed by a container mold. Theblow molding apparatus inflates the parison by forcing gas into theparison which causes the parison to stretch and take the shape of thecontainer mold. Once the parison has taken the shape of the containermold, the blow molding step is complete and the container is removedfrom the container mold for further processing.

In some applications of container manufacturing, a deep protrusion maybe required at a particular section of a container, for example, at abase or at a hand grip of the container. Deep protrusions, when locatedat the base of the container, are sometimes referred to as “push-ups”since the protrusions push up into the interior of the container.Employing known techniques to manufacture containers with deepprotrusions has various problems. One such problem is the lack oforientation of the plastic material around the deep protrusion, asdiscussed in more detail in U.S. Patent Application No. 60/671,459, theentire content of which is incorporated herein by reference.

There remains a need in the art, however, for an apparatus and methodfor forming blow molded plastic containers that include a deepprotrusion or other structure extending into the interior of thecontainer.

BRIEF SUMMARY OF THE INVENTION

According to one exemplary embodiment, the present invention relates toa base assembly for forming a base portion of a plastic container. Thebase assembly comprises a base pedestal, a base mold attached to thebase pedestal, a push rod movable between a first position and a secondposition with respect to the base mold to reposition a portion of theplastic container, and an activation mechanism adapted to move the pushrod between the first position and the second position.

According to another exemplary embodiment, the present invention relatesto a blow mold for a plastic container. The blow mold can comprise aplurality of mold portions together defining a cavity for a blow moldedplastic container, a push rod extending through at least one of the moldportions and movable between a first position and a second position withrespect to the at least one mold portion to reposition a portion of theplastic container; and an activation mechanism adapted to move the pushrod between the first position and the second position.

The present invention also relates to a method of blow molding a plasticcontainer. The method comprises (a) enclosing a parison within a moldcavity of a blow mold, (b) inflating the parison within the mold cavityto form a blow molded container having a movable region, and (c) movinga portion of the blow mold to reposition the movable region while theblow molded container is in the mold cavity.

Further objectives and advantages, as well as the structure and functionof preferred embodiments, will become apparent from a consideration ofthe description, drawings, and examples.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of a preferredembodiment of the invention, as illustrated in the accompanying drawingswherein like reference numbers generally indicate identical,functionally similar, and/or structurally similar elements.

FIGS. 1A-B are side views of a base assembly of a blow mold according toan exemplary embodiment of the present invention;

FIG. 2 depicts an exemplary blow wheel of a blow molding machine,including a plurality of the base assemblies of FIGS. 1A-B;

FIGS. 3A-B are side views of a base assembly of a blow mold according toanother exemplary embodiment of the present invention;

FIG. 4 depicts an exemplary blow wheel of a blow molding machine,including a plurality the base assemblies of FIGS. 3A-B;

FIG. 5 depicts a blow mold according to an exemplary embodiment of thepresent invention; and

FIGS. 6A-B depict a method of blow molding a plastic container accordingto an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention are discussed in detail below. Indescribing embodiments, specific terminology is employed for the sake ofclarity. However, the invention is not intended to be limited to thespecific terminology so selected. While specific exemplary embodimentsare discussed, it should be understood that this is done forillustration purposes only. A person skilled in the relevant art willrecognize that other components and configurations can be used withoutparting from the spirit and scope of the invention. All references citedherein are incorporated by reference as if each had been individuallyincorporated.

When forming a plastic container, it may be desirable to mold a movableregion of the container in an outwardly extending position, andsubsequently displace or invert the movable region into the interior ofthe container. This may be desirable, for example, to improve materialflow or physical properties of the container. The present inventionrelates to a method and apparatus for displacing or inverting such amovable region of a plastic container.

FIGS. 1A-B illustrate an exemplary embodiment of a base assembly 100 ofa blow mold, according to the present invention. FIG. 1A illustrates aside view of the base assembly 100 having a push rod 102 in a first, orretracted position, while FIG. 1B illustrates a side view of the baseassembly 200 with the push rod 102 in a second, or extended position. Aswill be described in more detail below, once the container is formed inthe blow mold, a moveable region of the container (e.g., the base) canbe repositioned from an outwardly protruding position to an inwardlyprotruding position (e.g., toward the interior of the container).

The base assembly 100 can include a base pedestal 104, a base plug 106,a centering pin 108, and push rod 102. The centering pin 108 can be usedto secure and position the base assembly 100 in a blow molding apparatus(not shown in FIGS. 1A-B). The base pedestal 104 can have any shape, solong as it is adapted to accommodate the push rod 102, and to connectwith the base plug 106. For example, as shown in FIGS. 1A-B, the basepedestal 104 can have a hollow central region dimensioned to accommodatethe push rod 102 and at least a portion of the associated activationmechanism (described below). In addition, the base pedestal 104 can havean upper region adapted to connect with the base plug 106. According toan alternative embodiment, the base plug 106 and the base pedestal 104can be a single apparatus. During blow molding, the base assembly 100can be raised to connect with other mold assemblies for blow molding acontainer, as described in more detail below. After the container isblow molded, the base assembly 100 can be lowered to release thecontainer.

The base plug 106 can include a base mold 110 defining a contact surface112 adapted to contact a parison material during blow molding of acontainer. According to one exemplary embodiment, the contact surface112 can include a cavity 114, an outer surface 116, and an end surface118 of the push rod 102. The contact surface 112 of the base mold 110can form the shape of at least part of the container base during blowmolding. In the exemplary embodiment shown, the contact surface 112 isshaped and configured to form a moveable region and a bearing surface ofa container base, however other configurations are possible. Furtherdetails on the base mold 110 and contact surface 112 are provided inU.S. Patent Application No. 60/671,459, the entire content of which isincorporated herein by reference.

The push rod 102 can comprise a cylindrically shaped rod that extendsthrough the base pedestal 104 and is movable with respect to the basemold 110. According to one exemplary embodiment, the push rod 102 can bea metal mold component. The base assembly 100 can include a bore havingone or more bushings 120, for example, ceramic bushings, that supportthe push rod 102 for sliding movement with respect to the base mold 110.Alternatively, the base assembly 100 can include linear bearings orother structures known in the art to support the push rod 102 formovement with respect to the base mold 110.

As described above, the end surface 118 of the push rod 102 can define aportion of the contact surface 112 of the base mold 110 when the pushrod 102 is in the first position (FIG. 1A). In the exemplary embodimentshown, the end surface 118 is adapted to form a dimple in the base ofthe container. According to this embodiment, the shape of the endsurface 118 is similar to a truncated cone, with the end of thetruncated cone including a portion 122 (shown in phantom lines in FIGS.1A-B). The section 122 may be concave, for example, to form a convexsection in the base of the container that extends downward away from thecenter of the container. Alternatively, the section 122 of the endsurface 118 may be flat or convex extending upward toward the center ofthe container. The push rod 102 can be used to reposition a moveableregion of the base from an initially outward protruding position to aposition within the container cavity, as will be discussed in moredetail below.

Still referring to FIGS. 1A-B, the base assembly 100 can include anactivation mechanism 130 that moves the push rod 102 between an initial,or first position, shown in FIG. 1A, and an extended, or secondposition, shown in FIG. 1B. For example, the activation mechanism canelevate the end surface 118 of the push rod 102 above the surface of thebase mold 110, as shown in FIG. 1R In the exemplary embodiment shown inFIGS. 1A-B, the activation mechanism 130 comprises an air cylinder 132,such as a double acting cylinder, connected to the push rod 102. The aircylinder 132 can include an output shaft 134 that is coupled to, orintegral with, the push rod 102. In the embodiment where the outputshaft 134 is coupled to the push rod 102, any number of connectors knownin the art may be used. For example, the output shaft 134 and push rod102 may be coupled using an internal or external threaded connection. Athreaded connection can advantageously allow the combined length of theoutput shaft 134 and push rod 102 to be varied, consequently allowingfor adjustment of the initial and extended positions of the push rod102. Alternatively, the output shaft 134 may be welded to or bonded tothe push rod 102. Other exemplary techniques for coupling the outputshaft 134 to the push rod 102 include pinning and press fitting.

According to the exemplary embodiment shown in FIGS. 1A-B, the aircylinder 132 can be partially or entirely located within a hollowcentral region 136 of the base pedestal 104, however the air cylinder132 can alternatively be located outside the base pedestal 104. The aircylinder 132 can be anchored to the base pedestal 104 by a base block138, for example, a pillow block or other known structure. One or moreshims (not shown) can be placed between the base block 138 and the basepedestal 104 to provide for adjustment of the initial and extendedpositions of the push rod 102. Additionally or alternatively, the baseblock 138 can itself include a mechanism for adjusting the initial andextended positions of the push rod 102. For example, the base block 138can include overlapping ramp surfaces (not shown) and a graduated screw(not shown) that cooperate to adjust the overall height of the baseblock 138, although other configurations are possible. Alternativeexemplary embodiments for connecting the air cylinder 132 to the basepedestal 104 include connecting the air cylinder 132 directly to thebase pedestal 104 (e.g., by screwing, pinning, press fitting, bonding,or welding), or forming a portion of the air cylinder 132 integrallywith a portion of the base pedestal 104.

The activation mechanism 132 can further include a pneumatic valve 140.Pneumatic valve 140 can be connected to the air cylinder 132 via one ormore conduits 142. By regulating the amount of air that passes from anexternal pressure source (not shown) to the air cylinder 132 via one ormore of the conduits 142, the pneumatic valve 140 can control themovement of the output shaft 134, and correspondingly, the movement ofthe push rod 102. Thus, the pneumatic valve 140 can be used to controlmovement of the push rod 102 between the initial and extended positions.It can also be used to control the stroke length of the push rod 102, aswell as the stroke speed and other parameters of the movement of thepush rod 102.

According to an exemplary embodiment of the present invention, the baseassembly 100 can be incorporated into a blow molding machine having anelectronic control device, such as a programmable logic controller, thatcontrols the movement of some or all of the components of the blowmolding machine. According to this embodiment, the pneumatic valve 140can be electrically connected to the electronic control device, suchthat the electronic control device controls the pneumatic valve 140 andthe resultant movement of the push rod 102.

According to another exemplary embodiment, the pneumatic valve 140 canbe controlled via mechanical means, for instance, on a blow moldingmachine that does not have an electronic control device, or in instanceswhere electronic control is not preferable. Referring to FIG. 2, aplurality of the base assemblies 100 can be located on a rotating blowwheel 300 of a blow molding machine. The pneumatic valves 140 can belocated around the periphery of the wheel 300. Each pneumatic valve 140can have a switch 144 (also shown in FIGS. 1A-B) that regulates movementof air through the pneumatic valve 140 and into the air cylinder 132.One or more cam members 302 can be located on or near the blow moldingmachine in a stationary manner with respect to the blow wheel 300. Wheneach respective base assembly 100 (and the attendant pneumatic valve 140and switch 144) rotates past the cam member 302, the cam member 302 canimpart movement to the switch 144 (e.g. depress the switch 144). Thismovement of switch 144 can for example, cause air to flow through thepneumatic valve 140 in a manner that causes the air cylinder 132 to movethe push rod 102 to the extended position. When the switch 144 movespast the cam member 302, the switch 144 can return to its originalposition (e.g., under the force of a spring), thereby changing orstopping the flow of air through the pneumatic valve 140, such that thepush rod 102 returns to its original position.

According to an exemplary embodiment, the position of the cam member 302with respect to the wheel 300 and/or switches 144 can be adjustable. Forexample, the cam member 302 can be mounted on a pair of shafts 304 thatare slidable in fixed anchors 306. Set screws (not shown) or other knownfasteners can be provided in the anchors 306 to lock the shafts 304 inthe anchors 306, thereby fixing the position of the cam member 302.Adjustment of the position of the cam member 302 with respect to theswitches 144 can advantageously provide for adjustment of the amount ofdepression of the switches 144, for example, to minimize wear on theswitches 144 or to adjust the stroke of the air cylinders 132.Additionally or alternatively; the adjustment may allow the cam member302 to be moved completely out of contact with the switches 144, forexample, to eliminate wear on the switches 144 and/or cam member 302during dry cycling of the machine.

Referring to FIGS. 3A-B, another exemplary embodiment of a base assemblyaccording to the present invention is shown. Except where indicatedotherwise below, the elements of base assembly 200 are similar to oridentical to the corresponding elements of base assembly 100, shown anddescribed above with respect to FIGS. 1A-B.

The base assembly 200 of FIGS. 3A-B can include an activation mechanism230 that utilizes one or more cam members to move the push rod 202between the initial position (FIG. 3A) and the extended position {FIG.3B). A first cam member 250 can be mounted in the base pedestal 204. Thefirst cam member 250 can include a cam surface 252 (e.g., an inclined orramped surface) that interacts with a cam follower (described below) toimpart movement to the push rod 202. The base assembly 200, andparticularly the base pedestal 204, can include one or more bushings254, for example, ceramic bushings, to support the first cam member 250for sliding movement with respect to the push rod 202. Alternatively,the base assembly 200 can include linear bearings or other structuresknown in the art to support the first cam member 250 for slidingmovement. In the exemplary embodiment shown in FIGS. 3A-B. the push rod202 moves along a first axis that is substantially aligned with thecentral axis of a container being formed, and the first cam member 250slides along a second axis that is substantially transverse to the firstaxis, however, other configurations are possible.

The push rod 202 can include a cam follower 256 that interacts with thecam first cam member 250 to impart movement to the push rod 202. In itssimplest form, the cam follower 256 can comprise the end of the push rod202. According to one exemplary embodiment, the end can be rounded toallow for smooth movement along the cam surface 252. According toanother exemplary embodiment, the earn follower 256 can comprise aroller 258 attached to the end of the push rod 202. In embodiments wherethe cam follower 256 comprises a roller 258, the push rod 202 andbearings 220 can have substantially matching cross-sections (e.g.,square) that prevent the push rod 202 from rotating about its axis withrespect to the base assembly 200, thereby preventing the roller 258 frombecoming misaligned on the cam surface 252.

The push rod 202 can be biased toward the initial position shown in FIG.3A. For example, a coil spring 260 can extend around the push rod 202between a surface 262 of the base pedestal 204, and a shoulder 264located on the push rod 202 proximate the cam follower 256, althoughother configurations are possible and will be apparent to those ofordinary skill in the art. The first cam member 250 can also be biasedtoward the position shown in FIG. 3A (corresponding to the initialposition of the push rod 202). For example, a coil spring 266 can extendaround the first cam member 250 between a surface 268 of the basepedestal 204, and a shoulder 270 located on the first cam member 250,however, other configurations are possible and will be apparent to thoseof ordinary skill in the art.

Movement of the first cam member 250 from the position shown in FIG. 3Ato the position shown in FIG. 3B causes the cam follower 256 to slidealong the cam surface 252, and correspondingly, move the push rod 202from the initial, or first position, to the extended, or second,position. Returning the first cam member 250 to the position shown inFIG. 3A causes the push rod 202 to return to its initial position shownin FIG. 3A, for example, under the force of spring 260, if provided.

The embodiment of FIGS. 3A-B has many components that are similar to, oridentical to, the embodiment of FIGS. 1A-B. One of ordinary skill in theart will know and appreciate that many of the components can beinterchanged between these exemplary embodiments with little or nomodification. For example, the push rod 102 of FIGS. 1A-B can bereplaced with for the push rod 202 of FIGS. 3A-B by changing thedimensions of the bushings 120 and the diameter of the bore in thepedestal 104. Likewise, the pushrod 202 of FIGS. 3A-B can be replacedwith the push rod 102 of FIGS. 1A-B by similarly re-dimensioning thebushings 220 and the bore in the pedestal 204. One of ordinary skill inthe art will recognize other components that can be interchanged betweenthe various embodiments, and these changes are contemplated by thepresent invention.

Referring to FIG. 4, a plurality of base assemblies 200 can be locatedon blow wheel 300. When each respective base assembly 200 rotates pastthe stationary cam member 302, the first cam member 250 of therespective base assembly 200 contacts the stationary cam member 302, andmoves from the position shown in FIG. 3A to the position shown in FIG.3B. As a result, the first cam member 250 moves the push rod 202 fromthe initial position (FIG. 3A) to the extended position (FIG. 3B). Oncethe respective base assembly 200 moves a sufficient distance past thestationary cam member 302, the first cam member 250 returns to itsinitial position (FIG. 3A) under the force of the spring 266. Similarly,the push rod 202 returns to its initial position (FIG. 3A) under theforce of spring 260.

The position of the stationary cam member 302 can be moved with respectto the blow wheel 300, as described above in connection with FIG. 2.This adjustment can be used, for example, to adjust the throw of thefirst cam member 250 and the corresponding stroke of the push rod 202.Additionally or alternatively, this adjustment may allow the stationarycam member 302 to be moved completely out of contact with the first cammembers 250, for example, to eliminate wear on the components of theactivation mechanism 230 and the stationary cam member 302 during drycycling of the machine. The stroke of the push rod 202 can also bevaried by changing the inclination of the cam surface 252 on the firstcam member 250.

Although the activation mechanisms 130, 230 have been described above asbeing external to the push rod 102, 202, they may alternatively belocated at least partially inside the push rod 102, as will be apparentto one of ordinary skill in the art.

Referring to FIG. 5, an exemplary blow mold according to the presentinvention is shown. The blow mold 400 comprises a plurality of moldportions that together define a cavity in which a plastic container isblow molded. The exemplary embodiment shown includes the following moldportions: a first side mold 402, a second side mold 404, and a baseassembly 100. One of ordinary skill in the art will know and appreciatethat base assembly 200 can alternatively be used in place of baseassembly 100. One of ordinary skill in the art will further know andappreciate that other base assemblies within the scope of the presentinvention can also be substituted for base assembly 100. A parison 406having a threaded finish is depicted as being attached to a holder 408.The first side mold 402 can contain a mold of one side of the container,and the second side mold 404 can contain a mold of the other side. Thefirst and second side molds 402, 404 may be mirror images of oneanother, or they may have different shapes. Other combinations anddifferent numbers of molds may be used, as will be understood by one ofordinary skill in the art.

Although the push rod 102 and activation mechanism 130 are shown in theexemplary embodiment of FIG. 5 as being associated with the baseassembly 100, one of ordinary skill in the art will know and appreciatethat a push rod and associated activation mechanism may be associatedwith any of the mold portions that comprise the blow mold 400. Forexample, a push rod and activation mechanism may be associated with thefirst side mold 402 or the second side mold 404, or both. In addition,one of ordinary skill in the art will know and appreciate that the blowmold 400 may include multiple push rods and activation mechanismsassociated with one or multiple mold portions.

Referring to FIGS. 6A-B, the present invention also relates to a methodof blow molding a plastic container. Prior to blow molding, a parison(for example, the parison 406 shown in FIG. 5) is enclosed in a moldcavity defined by the first side mold 402, the second side mold 404, andthe base mold 110. Although base assembly 100 and base mold 110 areillustrated in FIGS. 6A-B, one of ordinary skill in the art willrecognize that base assembly 200 and base mold 210 can alternatively beused, as can other base assemblies and/or base molds within the scope ofthe present invention. Once the parison is enclosed, gas can be forcedinto the parison to inflate the parison within the mold cavity. Duringinflation, the parison stretches into the form of the mold cavity toform a blow molded container. In the exemplary embodiment shown, as theparison material contacts the base mold 110, the parison material isblown against the contact surface 112 and into cavity 114 (see FIG. 6B),thereby forming moveable region 420 in the base of the container.Further details and variations of the blow molding process will beapparent to one of ordinary skill in the art, and are further providedin U.S. Patent Application No. 60/671,459, the entire content of whichis incorporated herein by reference.

After the container has been formed in the cavity, a movable portion ofthe blow mold can reposition the movable region of the container. Forexample, push rod 102 extending through the base mold 110 can move fromits first or initial position, shown in FIG. 6A, to its second orextended position, shown in FIG. 6B, to reposition the movable region420 in the base of the container. In the exemplary embodiment of FIGS.6A-B, the moveable region 420 of the container base protrudes outwardfrom the container and is downwardly convex prior to being repositioned.Movement of the push rod 102 upward toward the center of the containerexerts pressure on the moveable region 420 of the base, and forces themovable region 420 into an inwardly protruding position. After themoveable region 420 is repositioned upward, the push rod 102 may belowered. Thereafter, the side molds 402, 404, and the base mold 110 maybe separated, thereby releasing the container from the blow mold 400.

Movement of the push rod 102 from the first position to the secondposition, and back again, can be realized using the air cylinder 132 andrelated elements described above in connection with FIGS. 1-2. Accordingto this exemplary embodiment, the air cylinder 132 can be triggeredelectronically (e.g., via the blow molding machine's programmable logiccontroller), mechanically (e.g., via contacting switch 144 on pneumaticvalve 140 with a stationary cam member 302, as illustrated in FIG. 2),or using other structures and techniques known to one of ordinary skillin the art. Alternatively, movement of the push rod can be realizedusing a first cam member 250, and a cam follower 256 associated with thepush rod 202, as described in connection with FIGS. 3-4. The stationarycam member 302 can be used to trigger movement of the push rod 202, asshown in FIG. 4, however other configurations, manual, electronic, orother, are possible and contemplated by the present invention. People ofordinary skill in the art will know and appreciate that other structuresand methods can be utilized to move the movable portion of the blow mold(e.g., the push rod) between the first and second positions.

According to one exemplary embodiment of the invention, repositioning ofthe base can occur prior to removing the container from the blow mold,so that the container may be placed on a substantially flat surface fortransport to, for example, a filling machine, or alternatively, fortransport during manufacturing or for palletizing, as is known in theart. The filling machine may fill the container by any known fillingprocess, including hot filling, cold filling, and other fillingprocesses known by those skilled in the art. By repositioning themoveable region 420, the container can stand stably on a substantiallyflat surface and be processed similar to containers with conventionallymanufactured push-up bases. Further details of this aspect of theinvention are provided in co-pending International Application No.PCT/US2004/024581, the entire content of which is incorporated herein byreference.

According to another exemplary embodiment of the invention, blow moldingthe base in the outwardly protruding position and subsequentlyrepositioning it can result in a container having a deep protrusion orpush-up without the occurrence of decreased crystallinity and/or or thepresence of regions of thick, amorphous plastic, that are common inprior art forming methods. Further details of this aspect of theinvention are provided in U.S. Patent Application No. 60/671,459, theentire content of which is incorporated herein. by reference.

Although the figures of the present application illustrate the parison304 as a preform having threads at the top, the parison may also be athreadless plastic tube without departing from the scope of the presentinvention. One example using a parison that is a plastic tube involvesinserting a needle into the parison, and forcing gas through the needleto expand the plastic tube to take the shape of a mold. Additionally,any blow molding technique may be used for forming the container,including injection blow molding, stretch blow molding, or extrusionblow molding, as will be understood by those of ordinary skill in theart.

It is noted that the detailed description describes an exemplary methodfor blow molding a moveable region 420 on a container base. However,this technique may be used to form other regions of a container otherthan the base, such as to form at least a portion of a hand grip of acontainer, or to form other deep protrusions of a container. The cavity420 may also be located on either side mold 402, 404, or on otherlocations in the base mold.

The embodiments illustrated and discussed in this specification areintended only to teach those skilled in the art the best way known tothe inventors to make and use the invention. Nothing in thisspecification should be considered as limiting the scope of the presentinvention. All examples presented are representative and non-limiting.The above-described embodiments of the invention may be modified orvaried, without departing from the invention, as appreciated by thoseskilled in the art in light of the above teachings. It is therefore tobe understood that, within the scope of the claims and theirequivalents, the invention may be practiced otherwise than asspecifically described.

What is claimed is:
 1. A base assembly for a stretch blow moldingapparatus forming a base portion of a plastic container, the baseassembly comprising: a unified one-piece base pedestal; a unifiedone-piece base mold comprising at least one curved contact surface thatforms at least one downward convex cavity of said plastic containerattached to the base pedestal; a unified one-piece push rod movablebetween a first position and a second position with respect to theunified one-piece base mold to reposition a portion of the plasticcontainer; and an activation mechanism adapted to move the push rodbetween the first position and the second position, wherein said baseassembly is suitable for stretch blow molding.
 2. The base assembly ofclaim 1, wherein the activation mechanism comprises an air cylinderadapted to move the push rod.
 3. The base assembly of claim 2, whereinthe air cylinder comprises an output shaft connected to the push rod. 4.The base assembly of claim 2, wherein at least part of the air cylinderis located in the base pedestal.
 5. The base assembly of claim 2,wherein the activation mechanism comprises a pneumatic valve incommunication with the air cylinder and adapted to control movement ofthe air cylinder.
 6. The base assembly of claim 5, wherein the baseassembly is incorporated into a stretch blow molding machine having anelectronic control device, and the electronic control device controlsthe pneumatic valve.
 7. The base assembly of claim 2, located on arotating blow wheel of a stretch blow molding machine, wherein theactivation mechanism further comprises a switch located on the blowwheel and a stationary cam member located adjacent the blow wheel,wherein the switch and the cam member interact to control movement ofthe air cylinder.
 8. The base assembly of claim 1, wherein theactivation mechanism comprises a first cam member associated with theunified one-piece base pedestal, and a cam follower associated with theunified one-piece push rod.
 9. The base assembly of claim 8, wherein thecam follower comprises a roller attached to the unified one-piece pushrod.
 10. The base assembly of claim 8, wherein the cam followercomprises an end of the unified one-piece push rod.
 11. The baseassembly of claim 10, wherein the end of the unified one-piece push rodis rounded.
 12. The base assembly of claim 8, wherein the unifiedone-piece push rod is movable along a first axis substantially alignedwith the central axis of a plastic container being fanned, and the cammember is movable along a second axis substantially traverse to thefirst axis.
 13. The assembly of claim 8, wherein the unified one-piecepush rod is spring biased toward the first position.
 14. The baseassembly of claim 8, located on a rotating blow wheel of a stretch blowmolding machine, further comprising a stationary second cam memberlocated adjacent to the blow wheel, wherein the second cam member isadapted to impart movement to the first cam member to move the unifiedone-piece push rod between the first position and the second position.15. The base assembly of claim 1, wherein the unified one-piece push rodextends through an opening in the unified one-piece base mold.